Bobbin thread wiping device for lock stitch sewing machines



Oct. 1, 1963 5. J. KETTERER BOBBIN THREAD WIPING DEVICE FOR LOCK STITCH SEWING MACHINES IN VENT 0R. STANLEY J. KETTERER y ATTORNEY Filed Aug. 25. 1961 United States Patent ice 3,1li5,ei EEGEEIN THREAT: WEEPENG Di /16E FGR LGCK SIi'iQii SEWENG Staniey 3. Ketterer, Morris Plains, NJ assignor to "he Singer Company, a corporation of N w .iersey Filed Aug. 25, 1963, Ser. No. 133,877 2 (liaims. ill. 112-186} This invention relates to lock stitch sewing machines of the type in which thread may be replenished periodically on the bobbin in place in the loop taker, more particularly, to a novel device associated with mechanism adapted to withdraw unused thread from the bobbin preparatory to replenishment of a fresh bobbin thread supply, and specifically to a novel and improved device for engaging and wiping the thread being withdrawn from the bobbin to a position opposite the body of the loop taker.

It is an object of this invention to provide a bobbin thread wiping device which is positive in action and exceedingly reliable in constraining the thread being withdrawn from the bobbin in a predetermined position alongside the body of the loop taker so that the loop taker body will provide a drum about which the withdrawn thread is carried.

A further object of this invention is to provide a bobbin thread wiping device of the above character which is simple and economical to manufacture and which does not interfere with the bobbin thread replenishing or the sewing operations of the sewing machine.

In the accompanying drawings of a preferred embodiment of this invention:

FIG. 1 represents a side elevational view of a sewing machine loop taker with a fragment of the work supporting bed illustrated in cross section and including the bobbin thread wiping mechanism of this invention in a retracted position constraining the thread from the bobbin alongside the loop taker,

FIG. 2 represents an end elevational view of the loop taker and bobbin thread wiping mechanism of FIG. 1,

FIG. 3 represents a top plan view of the loop taker and bobbin thread wiping mechanism taken substantially along line 3-3 of F G. 1 immediate.y beneath the work supporting bed and illustrating the bobbin thread Wiper in extended position, and

FIG. 4 represents a detached top plan view of the bobbin thread wiping mechanism parts of PEG. 4 illustrating the bobbin thread 'wiper in retracted position.

This invention pertains to a lock stitch sewing machine of the type in which looking or bobbin thread may be replenished from the needle thread supply during normal lock stitch forming motions of the needle and loop taker. By stitch forming motions as hereinafter used in the specification and in the claims is meant those motions of the needle and loop taker which are required for the formation of lock stitches. The term stitch orming motion will be used as descriptive of the precribed motion of the needle and loop taker irrespective f whether thread is or is not present for concatenation thereby into stitches. The mechanism for replenishing the under or bobbin thread supply is not illustrated or described in detail herein, but may be of the form described in the copending United States patent application of S. I. Ketterer and W. 3. Edwards, No. 15,955 filed March 18, 1960, now Patent No. 3,063,392, granted November 13, 1962. This invention is particularly directed to a mechanism for withdrawing the under or locking thread from the bobbin at the completion of a stitching operation and in preparation for the succeeding under thread replenishing operation. This invention is an improvement of the mechanism illustrated 3,1b5fi5l Fatented Qct. 1, 1963 2 and described in the copending United States patent application of S. J. Ketterer, W. J. Edwards and M. Ivanko, Serial No. 12,828 filed March 4, 1960, now Patent No. 3,038,429, granted June 12, 1962.

As illustrated in the drawings, 11 indicates the work support of a sewing machine bed fitted with a throat plate 12 formed with a needle aperture 13. Journaled beneath the bed is a hollow loop taker drive shaft 14 to which is secured a loop taker indicated generally as 15. The loop taker is formed with a cup-shaped body portion 16 of substantially cylindrical form and having a needle loop seizing beak 17 formed thereon. An annular needle thread camrning member 18 is preferably secured to the outer periphery of the cylindrical body portion of the loop taker. iournaled within the cu shaped body portion is a bobbin carrying case 19 formed with a rotation restraining notch 23 which accommodates a rotation restraining finger 21 carried beneath the work supporting bed of the sewing machine to prevent the bobbin carrying case from turning with :the loop taker. A thread carrying bobbin 2% is freely journaled within the bobbin carrying case.

After thread has been replenished in the bobbin as for instance by the means illustrated in detail and described in the above referred patent application Serial No. 15,955, lock stitches (Federal type stitch No. 30 1) are formed by a needle 25 and loop taker, the loop seizing beak 17 of the loop taker seizing, expanding and carrying successive loops of the needle thread Tn completely about the bobbin carrying case so as to concatenate the needle and bobbin threads which are then withdrawn up into the work in the form of stitches. The bobbin thread during stitch formation issues from a slot 22 in the bobbin carrying case between the bobbin carrying case and a bobbin thread tensioning spring 23, about the free edge of the thread camming member- 13 on the loop takerv body portion, and thence upwardly through the needle aperture to the work. These parts thus constitute a means for determining a definite path of locking thread from the bobbin to the stitches being formed in the work.

When stitching operation nears completion, the bobbin thread extending from the work to the bobbin must be cleared from the bobbin so as to provide for reception of a fresh supply prior to the succeeding sewing operation. Unused tag end portions of bobbin thread if permitted to remain in :the bobbin would accumulate and eventually completely fill the bobbin leaving no space for reception of a fresh supply. The mechanism of this invention is directed to a means for withdrawing such unused bobbin thread end portions from the bobbin, and as will be apparent hereinbelow :this mechanism operates during the last cycle of stitch forming motion of the loop taker during each stitching operation.

Slidably supported beneath the work support 11 of the sewing machine bed is a slide bar 30 which, as illustrated and described in detail in the above referred patent application Serial No. 12,828, may be operated by a control mechanism such as a cam or the like so as to be shifted first in one direction, toward the left as illustrated in FIGS. 1 and 3, and then in the opposite direction, toward the right as viewed in FIGS. 1 and 3 during the last stitch forming cycle of the loop taker in stitching operation. Secured by fastening screws 31 to the slide bar 39 and disposed substantially parallel to the work support 11 is a plate 32 which is disposed behind the loop taker 15. The plate 32 carries a cam finger 33, Which when the slide bar 39 is shifted to the left as viewed in FIG. 3, abuts an annular spring member 34 secured at one side by a screw 35 to the loop taker body portion and formed when unconstrained to extend at an angle from the screw 35 outwardly from the loop taker body portion. Substantially diametrically opposite the screw 35 the annular spring member is embraced by the notched end portion 36 of an auxiliary hook member 37 slidably constrained in a transverse slot in the cylindrical body portion 16 of the loop taker and between the cylindrical body portion of the loop taker and the thread camming member 18 thereon. When the slide bar 30 is shifted to the left as viewed in FIG. 3 the cam finger 33 in abutting the annular spring member serves to shift the auxiliary hook member from a retracted inoperative position beneath the thread camming member lid into an extended position in which the auxiliary hook member will traverse the path of bobbin thread from the' bobbin to the work and thus seize and draw out the bobbin thread in a loop which will initially follow substantially the periphery of the loop taker body portion.

Also secured on the plate 32 carried on the slide bar 30, as by a fastening screw 38 and a locating pin 3? is a thread wiping arm 4% which is disposed as illustrated in FIG. 2 on that side of the needle aperture 13 in the throat plate toward which faces the loop seizing beak 17 and the auxiliary hook member 37. 'ilie free extremity of the auxiliary member is formed with a downturned and slightly inturned thread gripping finger 41. When the slide bar 39 is shifted to the leftas viewed in PEG. 3, the thread gripping finger will be shifted into extended position as illustnated in dashed lines in FIG. 1 and in solid lines in H6. 3 in a position extending across that limb of the bobbin thread loop which is seized by the auxiliary hook. The thread Tb illustrated in FIG. 3 is the bobbin thread which has been seized by the auxiliary hook 37. FIG. 3 thus illustrates the manner in which the thread wiping arm 4%) is shifted to an extended position spanning the bobbin thread Tb.

The slide bar 3% is preferably shifted toward the right as viewed in FIG. I soon after the auxiliary book has engaged and has begun to draw out loops of the bobbin thread, that is, the movement of the slide bar 3% to the right preferably begins in the position of parts illustrated in FIG. 3. In moving to the right with the slide bar 39 the thread gripping finger 41 will engage and carry that limb of the loop of bobbin thread formed by the auxiliary hook member 37 to a position opposite the substantially cylindrical body portion 16 of the loop taker and of the substantially cylindrical thread carnming member 18 carried thereon. In order to prevent the bobbin thread from slipping off the thread gripping .finger 41, a keeper member 42 is secured beneath the work support 11 by screws 43. The keeper member extends at one side of the needle aperture in the throat plate and is formed with an abutment surface 44 disposed contiguous to the thread gripping finger 1 in the retracted position of the thread gripping finger, that is, when the slide bar has been shifted to the right as viewed in FIGS. 1 :and 3 and the said abutment surface 44 being substantially parallel to the path of motion of the slide bar 3t? and thread gripping finger 41.

When the tag end'of thread from the bobbin is to be removed at-the conclusion of stitching, the motion of the slide bar 30 to the leit thus shifts the thread gripping finger 41 into an extended position away from the abutment surface on the keeper member and simultaneously renders the auxiliary hook member 37 effective to engage the bobbin thread. After the bobbin thread has been engaged and slightly drawn out by the auxiliary hook member as illustrated in FIG. 3, the motion of the slide bar 39 to the right shifts the thread gripping finger 41 into the retracted position contiguous to the abutment surface on the keeper member thus positively constraining the tag end of bobbin thread opposite the portion of largest diameter on the loop taker. Continued circular motion of the auxiliary hook member can thus serve to draw out the tag end of thread from the bobbin with the peripheral body portion of the loop taker serving as a drum so as to accommodate the largest possible length of unused bobbin thread. The combination of the thread engaging finger 41 with the keeper member 42 provides for positively constraining the tag end of bobbin thread in a position alongside the loop taker body portion more advantageous to successful removal from the bobbin.

The rotary loop taker 15 is preferably of the type which partakes of stitch forming motion comprising two rotations for each reciprocation of the needle, with needle loop seizure by the beak l7 occurring every other rotation of the loop taker. The above described withdrawal of the tag end of bobbin thread Tb preferably begins during an idle rotation of the loop taker prior to the last needle loop seizure by the beak 17 in a cycle of sewing operation. As illustrated in FIGS. 1 and i2, subsequent to withdrawal of the tag end of bobbin thread Tb seizure of a loop of needle thread Tn occurs for the purpose of carrying down the needle thread so that it may be severed with the withdrawn tag end of bobbin thread closely beneath the work fabrics.

Having thus set forth the nature of the invention, what 1 claim herein is: V

l. A thread wiping mechanism for a lock stitch sewing machine having a Work support, a loop taker carried beneath said work support, a substantially cylindrical body portion formed on said loop taker, means for imparting circular stitch forming motion to said loop taker, a thread carrying bobbin journaled in said loop taker, a hook beak carried on said loop taker for engaging and carrying loops of sewing thread about said bobbin in the formation of lock stitches, means on said loop taker for determining a path or a locking thread from said bobbin to the stitches in a work fabric 'on said work support, and means for removing a locking thread from said bobbin during stitch forming motion of said loop taker including an auxiliary hook carried by said loop taker for circular movement there-With, means shifta-bly supporting said auxiliary hook for movement relatively to said loop taker into and out of an operative position in said path of the locking thread from said bobbin to the stitches in a work fabric on said work support, and means for shifting said auxiliary hook into and out of said operative position, said thread wiping mechanism comprising, a thread wiping arm formed with a depending thread gripping finger, means shiftably supporting said thread wiping arm between said loop taker and said work support, means for shifting said thread wiping arm in a direction substantially parallel to the axis of circular motion of said loop taker to position said thread gripping finger selectively in an extended position at one side of said loop taker body portion or in a retracted position radially outward of the cylindrical body portion of said loop taker, ad a member fixed relatively to said work support and formed with an abutment surface disposed radially outward of the cylindrical body portion of said loop taker and contiguous to said thread gripping finger in the retracted position thereof.

2. In a thread wiping mechanism as set forth in claim 1, means for shifting said. auxiliary hook into operativ position and simultaneously shifting said thread grippin finger into said extended position, and means for shifting said thread gripping finger into said retracted position contiguous to said abutment surface after said auxiliary book has carried said locking thread onto said thread gripping finger. 7

Dorsey Oct. 28, 1913 iohnson Aug. 16, 1960 

1. A THREAD WIPING MECHANISM FOR A LOCK STITCH SEWING MACHINE HAVING A WORK SUPPORT, A LOOP TAKER CARRIED BENEATH SAID WORK SUPPORT, A SUBSTANTIALLY CYLINDRICAL BODY PORTION FORMED ON SAID LOOP TAKER, MEANS FOR IMPARTING CIRCULAR STITCH FORMING MOTION TO SAID LOOP TAKER, A THREAD CARRYING BOBBIN JOURNALED IN SAID LOOP TAKER, A HOOK BEAK CARRIED ON SAID LOOP TAKER FOR ENGAGING AND CARRYING LOOPS OF SEWING THREAD ABOUT SAID BOBBIN IN THE FORMATION OF LOCK STITCHES, MEANS ON SAID LOOP TAKER FOR DETERMINING A PATH OF A LOCKING THREAD FROM SAID BOBBIN TO THE STITCHES IN A WORK FABRIC ON SAID WORK SUPPORT AND MEANS FOR REMOVING A LOCKING THREAD FROM SAID BOBBIN DURING STITCH FORMING MOTION OF SAID LOOP TAKER INCLUDING AN AUXILIARY HOOK CARRIED BY SAID LOOP TAKER FOR CIRCULAR MOVEMENT THEREWITH, MEANS SHIFTABLE SUPPORTING SAID AUXILIARY HOOK FOR MOVEMENT RELATIVELY TO SAID LOOP TAKER INTO AND OUT OF AN OPERATIVE POSITION IN SAID PATH OF THE LOCKING THREAD FROM SAID BOBBIN TO THE STITCHES IN A WORK FABRIC OIN SAID WORK SUPPORT, AND MEANS FOR SHIFTING SAID AUXILIARY HOOK INTO AND OUT OF SAID OPERATIVE POSITION, SAID THREAD WIPING MECHANISM COMPRISING, A THREAD WIPING ARM FORMED WITH A DEPENDING THREAD GRIPPING FINGER, MEANS SHIFTABLY SUPPORTING SAID THREAD WIPING ARM BETWEEN SAID LOOP TAKER AND SAID WORK SUPPORT, MEANS FOR SHIFTING SAID THREAD WIPING ARM IN A DIRECTION SUBSTANTIALLY PARALLEL TO THE AXIS OF CIRCULAR MOTION OF SAID LOOP TAKER TO POSITION SAID THREAD GRIPPING FINGER SELECTIVELY IN AN EXTENDED POSITION AT ONE SIDE OF SAID LOOP TAKER BODY PORTION OR IN A RETRACTED POSITION RADIALLY OUTWARD OF THE CYLINDRICAL BODY PORTION OF SAID LOOP TAKER, AND A MEMBER FIXED RELATIVELY TO SAID WORK SUPPORT AND FORMED WITH AN ABUTMENT SURFACE DISPOSED RADIALLY OUTWARD OF THE CYLINDRICAL BODY PORTION OF SAID LOOP TAKER AND CONTIGIUOUS TO SAID THREAD GRIPPING FINGER IN THE RETRACTED POSITION THEREOF. 